To be improved Very detailed, showing exactly in front of which train door the correspondence or exit will be, or showing the exit's numbers as they are marked by RATP. Needs serious improvements, though: - not at all optimized for tablets (ugly low resolution) - only a small part of RER trains' stations is covered (those most commonly used in Paris) - some buttons overlap (e.g. when selecting the RER line on a tablet) If the above problems are resolved, the app will get 5 from me. For now it's 3.